“Despite the enormity of the problem, surveys of pesticide use have been few and far between, and much of the information to date has been mostly anecdotal,” says World Bank economist Susmita Dasgupta, who has been working to fill this gap in Bangladesh and Vietnam.

Dasgupta and a team of researchers in the World Bank’s Development Research Group have assembled and analyzed detailed survey data from these countries on the risk perceptions of pesticide users, their pesticide-handling behavior, and the effects of pesticides on their health.

The research offers simple, hands-on methodology to identify toxic hotspots in any developing country in the absence of detailed information on pesticide use. In addition, it analyzes the potential adoption of safer production methods.

Evidence from Bangladesh: Too much use, too little protection

In a recent survey of 820 boro (winter rice), potato, bean, eggplant, cabbage, sugarcane and mango farmers in Bangladesh, more than 47 percent of farmers were found to use more pesticides than needed to protect their crops.

With only four percent of farmers formally trained in pesticide use or handling, and over 87 percent freely admitting that they used little or no protective measures while applying pesticides, overuse is potentially a very threatening problem to farmer health as well as the environment.

Farmers identified pesticide traders as one of their main sources of information. However, 54 percent of the traders themselves reported frequent health symptoms commonly associated with acute pesticide poisoning and 92 percent freely admitted that they did not take any protective measures while handling pesticides. Clearly, there are large information gaps in the supply chain of pesticide use.

“But this problem is hardly confined to Bangladesh, where in fact we have been working with local groups to come up with solutions,” says Dasgupta. “Overuse and other pesticide-related problems are common in the developing world, though the extent may vary across countries.”

This research brings to light a range of policy implications. In Bangladesh, for instance, there is an urgent need to actively promote safer pesticide use and hygienic practices among people who handle these substances.

Research findings also highlight the need for policymakers to design effective, targeted outreach programs that address pesticide risk, safe handling, and protection. The approach should ideally be participatory, with a view to addressing the most dangerous information gaps.

Overuse is high in specific crops and regions

Another important finding from Bangladesh, and also Brazil, is that specific crops and geographic locations experience more overuse than others. For the most measurable results, interventions should focus on these crops and regions.

Pesticide use in Brazil, for instance, is heavily skewed towards a few cash crops: soybeans, sugarcane, cotton, fruits and tobacco for export. Policies targeted towards these crops may help sustainable development in Brazil.

These could include strict enforcement of existing regulations, farmer education and training, integrated pest management programs, or research on alternative crop-specific pest control methods.

Information on how pesticides affect health is quite limited in many developing countries, with many surveys relying solely on farmers’ self-assessments of their health status.

To test the reliability of self-reported data, Dasgupta and team conducted an acetyl cholinesterase enzyme (AChE) blood test for 190 rice farmers in Vietnam’s Mekong Delta.

Results reveal a high prevalence of pesticide poisoning—more than 35 percent of the tested farmers experienced acute pesticide poisoning and 21 percent were chronically poisoned.

But the link between symptoms that the farmers reported and the actual clinical results was very weak. Again, this study was conducted in Vietnam, but problems such as this are common across the developing world.

This finding highlights the fact that farmers are often unable to distinguish the symptoms of pesticide poisoning from other health problems, and suggests that regular medical checkups and blood tests should be conducted for those who handle highly or moderately toxic pesticides.

Also, farmers should be encouraged to switch to lower-hazard pesticides and use protective gear to reduce individual health risks.

“Even when individual farmers are careful, pervasive contamination from others’ pesticide use and persistent pesticide residues in local water, air and soil may pose significant health risks,” warns Dasgupta. “Collective measures are an important complement to individual actions.”

Environmental pollution: not just a local problem

Chemically polluted runoff from fields has contaminated surface and ground water, damaged fisheries, and destroyed freshwater ecosystems. It has also created growing "dead zones" in parts of oceans close to river mouths that drain agricultural regions.

Local agricultural pollution also has global effects. For example, toxic compounds from pesticides accumulate in oceanic food chains. Even the tissues of land mammals in "pristine" polar regions now contain significant toxic accumulations.

Alternative production methods: what works

Dasgupta and team compare outcomes for farming with Integrated Pest Management (IPM) and conventional techniques, using input-use accounting, conventional production functions and frontier production estimation.

IPM comprises a range of approaches, from carefully targeted use of chemical pesticides to biological techniques that use natural parasites and predators to control pests.

Results from Bangladesh suggest that the productivity of IPM rice farming is not significantly different from the productivity of conventional farming. Since IPM reduces pesticide costs with no accompanying loss in production, it seems to be more profitable than conventional rice farming.

Interview results also suggest substantial health and ecological benefits. However, collective adoption of these methods is a must. Neighbors’ continued reliance on chemicals to kill pests will also kill helpful parasites and predators, as well as exposing IPM farmers and local ecosystems to chemical spillovers from adjoining fields.